This paper presents a novel and efficient method for generating three-dimensional (3D) mesoscale structures of concrete using the discrete element method (DEM). The proposed approach enables the flexible and precise simulation of various aggregate shapes and volume fractions, which is crucial for sensitivity analysis and computational studies. Unlike traditional digitalization methods, this technique focuses on creating adjustable synthetic models to investigate the impact of different parameters on the mechanical properties of concrete. This technique demonstrates significant advantages in generating complex concave aggregates and high aggregate volume fraction models while allowing for flexible control of particle spacing, thus enhancing computational efficiency and model accuracy. Numerical simulations using the proposed method show excellent agreement with laboratory experimental results, validating its reliability. This method not only facilitates deeper sensitivity analysis but also aids in optimizing concrete designs and applications by providing insights into the effects of various parameters on concrete performance.

Pressurized water pipelines buried in an urban environment are prone to bursting failures, threatening public safety and traffic convenience. The limited studies in literature just focused on soil fluidization while few studies considered ground failure, shear strain, soil erosion and the influence of leakage locations during pipe bursts. In this study, extensive experimental tests along with a finite difference method - discrete element method (FDM-DEM) solid-fluid coupling analysis were conducted to investigate these issues. It was disclosed that the failure development during pipe bursts can be divided into three stages, i.e., seepage diffusion, erosion cavity expansion, and soil fluidization. By digital image correlation (DIC) analysis of the experimental results, a wedge-shaped displacement zone in ground was identified, with peak shear strain near its boundaries. Moreover, it was revealed that leakage locations affected the expansion origin of erosion cavity; as the burial depths increased, the ground heave range increased linearly; the maximum water outflow distance was closely related to the internal pressures of buried pipeline, which could be modeled by a square root formula based on turbulent jet theory. Mesoscopic analyses revealed that finer particles were more susceptible to erosion during pipe bursts because of the low possibility of forming strong connections with surrounding particles. The findings yielded from this study can enhance the understanding of pipe bursts and help professionals mitigate potential damage.

Introduction The engineering geological characteristics of Yunnan's lateritic soil are quite unique, making it prone to shallow group landslides under rainfall conditions. This study focused on an old lateritic soil landslide as a case study.Methods Soil column ponding infiltration experiment was conducted to investigate the infiltration behavior of the lateritic soil. Numerical simulation software was employed to analyze the rainfall-induced seepage characteristics of the landslide, and a comprehensive assessment of the failure mechanisms of the lateritic soil landslide was conducted.Results The study findings are as follows: (1) During water infiltration, the infiltration time curve of the lateritic soil column showed a parabolic growth trend. The migration rate of the wetting front rapidly decreased from 0.15 to 0.2 cm/min to 0.1 cm/min and then stabilized at approximately 0.04 cm/min. (2) Long-term heavy rainfall is the condition for the formation of this old lateritic soil landslide. By coupling the seepage process, the stability coefficient of the lateritic soil slope was calculated, revealing that the instability rainfall threshold of the slope under prolonged rainfall conditions is generally 120 mm/d. (3) The main changes in the seepage field occurred in the shallow soil layer. In the later stages of rainfall, the infiltration rate of the slope was controlled by the permeability coefficient of the lateritic soil. As the rainfall intensity increased, the depth of rainfall impact increased, and the pore water pressure in the shallow soil layer tended to gradually increase and then stabilize under different rainfall intensities. (4) Under long-term rainfall conditions, the volumetric water content of the soil at the toe of the lateritic soil slope first peaked. After the rainfall ended, moisture in the slope continued to migrate to the toe, keeping the soil at the toe in a saturated state. (5) The formation and evolution of this lateritic soil landslide could be divided into five stages: initial natural stage, rainfall infiltration-crack expansion, shallow creep-progressive collapse of the front edge, sliding surface penetration-overall instability, and landslide braking accumulation.Conclusion The research results provide significant theoretical guidance and practical implications for understanding the causes and prevention of lateritic soil landslides in similar areas.